How do you choose a turntable ?

OP, ..."ghdprentice, you approach it as a scientist or/and an engineer." 

Guilty as charged. I am trained as a scientist and worked as one for a decade and worked as an engineer for a while. So I approach things methodically. 

Depends on what level of turntable you are purchasing. Nuances/subtleties are magnified on a higher resolving system. Turntables all have a house sound. Clearaudio, Rega and VPI will all sound different with the same implemented components.

" Everything should be as simple as possible, but not simpler." Albert Einstein.

Turntable is a seemingly simple thing, it's not tape deck. That's the advantage of it. Well designed and made table can last for decades with minimal care. Might have to replace a motor. Decks can and do last for decades as well, not with minimal care, though.

I thought about it too. That turntables don't sound the same.

In a perfect world, when choosing a turntable I would compare its sound with Studer deck. The one that would come closest would win.

I agree that setting up a turntable can be a daunting experience.
 

I decided a while ago, to become a “student” of the process. I bought a used smartractor, a mini microscope and an azimuth block with grid lines. 
 

Understanding VTF, VTA, rake angle, azimuth, overhang etc will allow you to understand which attributes contribute to the sound you are looking for. 
 

Then find a turntable and arm combination that allows for easy adjustment of these parameters. 
 

I still worked with my audio dealer, but instead of relying on him for everything, I learned how to be self  sufficient. I believe I get better sound from my turntable as a result.